The present invention relates, in general, to transverse pressurization contour (TPC) sliders and methods for making the same. More particularly, the present invention relates to a TPC slider structure for use in conjunction with a computer storage device transducer in rotary actuated disk drives which exhibits controllably uniform flying height in relationship to a rotating storage medium and provides simplified manufacturability with enhanced reproduceability.
In a computer mass storage device incorporating a rotating storage medium, such as a rigid, fixed or "hard" disk drive, a transducer is caused to be positioned adjacent the surface of the storage medium to read and/or write data therefrom or thereto. The transducer or "head" can be inductive (comprising a coil wrapped around a ferrite or permalloy core) or thin film (constructed through photolithographic techniques) incorporating either inductive or magnetoresistive principles of operation. In addition to reducing track widths on the rotating storage medium, thin film heads help increase bit density due to the fact that their magnetic gaps have more consistent size and shape than can be achieved with inductive technologies. Moreover, due to their more tightly coupled nature, thin film heads deliver greater output (larger amplitude pulses) as the head passes over the medium. The higher bit density achievable of necessity implies very small head gaps and concomitantly low "flying" heights. Flying heights on the order of about four micro inches or less are achievable with present day technologies.
In order to cause the head to fly on an air bearing adjacent the surface of the medium, it is generally mounted to (or in the case of older composite heads formed with) a slider. The slider facilitates the formation of a generally uniform air bearing between the transducer or head and the rotating disk surface.
With prior art linear actuator disk drives, the slider maintains a somewhat linear flying height above the surface or the storage media due to the fact that it maintains a constant skew angle with respect to the rotating disk surface by its constant radial position with respect to the direction of rotation. Fluctuations in flying height then are due primarily to the higher relative disk speed at its outer diameter (OD) than at its inner diameter (ID) and the tendency to fly lower at the ID that this induces.
More modern rotary actuated disk drives place additional demands on slider configuration inasmuch as a relatively constant flying height must be maintained while the slider undergoes sharp lateral accelerations due to seeking (thus changing its skew angle to the direction of rotation) as well as encountering the differing relative velocities of the disk surface at its outer and inner diameters. Flying heads close to a rotating disk surface with extreme lateral accelerations due to seek operations requires not only very flat media surfaces, but also a very stiff air bearing for slider stability. Moreover, it can be seen that as with the linear actuator disk drives, the velocity of the slider over the outer diameter of a disk drive will be greater than at its inner diameter since the angular velocity of the rotating disk medium again, remains constant. In this regard, the slider will also tend to fly higher at the disk outer diameter and, conversely, lower at the disk inner diameter.
In an attempt to solve the problems attendant the requirements of maintaining generally uniform flying height of a read/write head in a rotary actuated disk drive despite lateral accelerations due to seek operations and relative radial positions with respect to the outer and inner diameters of the disk drive, a transverse pressurization contour (TPC) slider has been proposed. Such TPC sliders have been described in: White, J. W.,: "A Uniform Flying Height Rotary Actuated Air Bearing Slider", IEEE Transactions on Magnetics, Vol. MAG-22, No. 5, September 1986, pp. 1028-1030; U.S. Pat. No. 4,673,996 issuing to White for "Magnetic Head Air Bearing Assembly Utilizing Transverse Pressurization Contours"; and U.S. Pat. No. 4,870,519 issuing to White for "Uniform Flying Height Slider Assembly with Improved Dynamic Air Bearing Characteristics".
Many of the difficulties encountered in trying to obtain a uniform flying height profile over a wide range of skew angles and rotating disk radii have been addressed through the use of the TPC slider described in the prior art. However, the accompanying problem of accommodating large manufacturing tolerances in the manufacturing of TPC slider has not been fully addressed. That is, if one were to attempt to define the TPC rail widths of such a slider with conventional sawing techniques, lateral mispositioning of the saw can cause a wide variation in the effective angle (as defined in the aforementioned patents) of each TPC slider. As new sliders are designed to fly lower and lower (that is, closer to the rotating disk surface), the main air bearing surface ("ABS") portion of the rails gets narrower and the effect of a mispositioned cut on the effective TPC angle becomes greatly magnified, especially if TPC widths are scaled down the same as the other slider dimensions. Prior art TPC references have heretofore specified a total TPC width occupying from approximately 10% to 50% of the rail surface.
In addition, defining TPC width dimensions through the use of photolithographic techniques along with chemical etching, reactive ion etching or ion milling, while offering more precision than saw cutting, are nonetheless very time consuming, with the time required to perform the etch or milling operation being proportional to the desired depth. With conventional TPC sliders, the extra time, photomasking step and photoresist thicknesses required to form an ambient pressure slot between the ABS/TPC rails limits the desirability of such methods for manufacturing a TPC slider.